1. Field of the Invention
The preset invention generally relates to systems and method for rendering flows and volumes.
2. Description of the Known Technology
Flow simulations are used in different areas of science for various applications: from studying the flow around experimental aircrafts to analyzing cloud formation by air flow simulation. One critical, but difficult stage in the simulation process is analysis. Visualization is a key method for analyzing the simulation results and for providing meaningful feedback. As computational capabilities have increased in power and decreased in cost, the visualization community has faced significant challenges as the size, dimensionality and complexity of the simulation data has increased. Particularly, the simple step up from two-dimensional flow simulations to three-dimensional has rendered many existing flow visualizations techniques difficult to use. These techniques, when applied to three-dimensional flow data, tend to produce cluttered and hard-to-understand images.
In recent works, we have seen the dramatic use of illustrative techniques applied to three dimensional flow datasets. The usage of these illustrative effects has been very effective in removing the usual clutter associated with three-dimensional flow visualizations. However, the approach has been limited to regular rectangular grids because the data was being converted to three-dimensional textures and rendered using hardware accelerated texture-based volume rendering.
Flow visualization has received a lot of attention during past years, resulting in development of various techniques: vector glyphs, line integral convolution, texture advection and stream tracing (particle tracing, streamlines, and streaklines). While many of these techniques are effective for two-dimensional flows, the density of their representation often severely limits their effectiveness for three-dimensional flows, particularly in viscous flows and those containing boundary layers.
Illustration has also been considered as a viable approach to improve the understanding of flow volumes, showing the potential of applying volume illustration techniques to scalar flow volumes and streamlines. One recent achievement in computer graphics and visualization is the ability to render datasets interactively by utilizing the graphic processing units (“GPUs”) on personal computer (“PC”) graphics cards. A number of works have been focused on extending the existing techniques onto the GPUs.
Flow simulations very often produce regions in the volume that have finer grained detail than others. This is particularly true of viscous simulations or those that have boundary layer properties. For instance, we can be interested in the overall flow around an aircraft, but the particular details at the aircraft boundary are very important and need to be tracked. One common method for generating these simulations is by exploiting the positive aspects of non-regular grids. These grids allow small cells to be clustered in the boundary layer, and provide transitional cells to the far field where there is less need for fine grain detail and structure. Visualizing these grids, however, require methods that operate directly on the unstructured cells, rather than relying on resampling. Visualization techniques that operate on non-regular grids do not map directly to GPU textures. With general availability of graphics hardware acceleration, the respective works took advantage of GPU capabilities in the algorithm's implementation. The pre-integrated approach has improved the algorithm by using high-precision frame buffer blending].
However, these previous systems are limited to applying these techniques to uniform grids. Unstructured grids have emerged as a common basis for computing flow simulations. Therefore, there is a need for a system and method for applying and extending the flow illustration approach to tetrahedral meshes using pre-integrated GPU-accelerated raycasting.